Characterization of Cu Nanoparticles on TiO2 Photocatalysts Fabricated by Electroless Plating Method

Cu-modified TiO₂ photocatalysts (Cu/TiO₂) were fabricated by electroless plating and wet impregnation methods. Photocatalytic activity for H₂ production over Cu/TiO₂ by electroless plating method was higher than that over Cu/TiO₂ by impregnation method. Characterization of Cu nanoparticles by HRTEM, STEM-EDX, XRD and XAFS was studied. As compared to the wet impregnation method, the electroless plating method resulted in the formation of Cu nanoparticles with small size and uniform distribution on the TiO₂ surface, which caused the enhancement of H₂ production. XAFS measurement provided the evidences for the chemical state change of Cu species during the photocatalytic reaction. The process that Cu species varied from Cu²⁺ into Cu⁰ via Cu¹⁺ as the intermediate under photoirradiation is very important for the H₂ production, which indicates that the metallic Cu nanoparticles acted as the active sites and restrained the photogenerated charges recombination.     

Prediction of Residual Stresses Using Partial Least Squares Regression on Barkhausen Noise Signals

Residual stresses are quantitatively predicted based on the Barkhausen noise measurement with a partial least squares regression model. The measurements are taken from two sets of case-hardened samples. The benefits of using certain feature elimination strategies prior model identification are also studied. The elimination methods applied are correlation-based elimination, uninformative variable elimination and successive projections algorithm. The results show that the best predictions are usually obtained when the successive projections algorithm is applied. The prediction accuracy of the best models found shows that partial least squares models can be successfully used for prediction of material properties based on the Barkhausen noise measurement.     

Analysis of energy service systems in urban areas and their CO2 mitigations and economic impacts

Three kinds of energy service system were examined as alternative energy systems in urban areas. A comparison of these energy systems was performed by finding Pareto optimum solutions for a multi-objective model. The model had two objective functions: CO₂ emission and cost to consumer. Various energy pricings were provided in the model as variables.     

Analysis of energy pricing in urban energy service systems considering a multiobjective problem of environmental and economic impact

Introduction of an integrated energy service system in an urban area is assumed. An energy supply plant is installed in the area to provide integrated energy service. It supplies electricity, gas, cooling, and heating to consumers. To consider CO/sub 2/ emission constraint in the area, analyses of energy pricing, economic impact on energy consumers, and operation of the system under the constraint of CO/sub 2/ emission were performed. CO/sub 2/ emission and economic impact on the consumers and the supplier of various energy pricing scenarios were calculated using linear programming models. The solution that satisfied the CO/sub 2/ emission restriction, and was economically optimal to the consumers was chosen from the results. The chosen solutions are Pareto optimum solutions of a multiobjective problem that concerns both CO/sub 2/ emission and cost to the consumers.     

Size Controlled Synthesis of Gold Nanoparticles by Porphyrin with Four Sulfur Atoms

Tetradentate thioacetyl porphyrin ligand (1) was synthesized to protect gold nanoparticles. 1-protected gold nanoparticles were characterized by UV-vis spectroscopy and XPS. Analysis by XPS showed that all of four thioacetyl groups of 1 were dissociated and bound to the surface of gold nanoparticles in thiolate form. The size of 1-protected gold nanoparticles (GN:1) was controlled by thioacetyl group/HAuCl₄ molar ratio and approached to 2 nm. Compared with a protecting ligand without porphyrin plane (2) or dodecanethiol, 1 can control the size of gold nanoparticles efficiently probably due to the tetradentate ligation effect.     

Dynamic in situ observation of automotive catalysts for emission control using X-ray absorption fine structure

Two main pivotal subjects of research in automotive catalysts were studied by modern X-ray absorption analysis techniques. One is oxygen storage/release behaviour, and the other is sintering inhibition of Pt particles. First, three types of CeO₂–ZrO₂ (Ce:Zr = 1:1 molar ratio) compounds with different oxygen storage/release capacities and different structural properties were prepared, and the valence change of Ce as a function of temperature during oxygen release/storage processes was investigated. The reduction of surface Ce mainly occurred in the range 100–170 °C, and the reduction of bulk Ce progressed at high temperatures of 170 °C and above. The Ce reduction behaviour depended not only on the homogeneity of the Ce and Zr for bulk reduction at high temperatures but also on the particle size of the CeO₂–ZrO₂ samples for surface reduction at low temperatures. Secondly, sintering inhibition of Pt in Pt/Al₂O₃, Pt/MgO and Pt/ceria-based catalysts after 800 °C ageing in air was studied. We found that the Pt–O–M (M = Mg, Ce) bond acted as an anchor and inhibited the sintering of Pt particles on MgO or ceria-based oxide. Especially, it was noteworthy that the Pt–O–Ce⁴⁺ bond on the ceria-based support breaks easily through the reduction of Ce (Ce⁴⁺ → Ce³⁺) during the usual stoichiometric and reducing conditions.     

Analyzing the Boundary Thermal Resistance of Epitaxially Grown Fe<Subscript>2</Subscript>VAl/W Layers by Picosecond Time-Domain Thermoreflectance

To gain deep insight into the mechanism of phonon scattering at grain boundaries, we investigated the boundary thermal resistance by using picosecond pulsed-laser time-domain thermoreflectance for epitaxially grown W/Fe₂VAl/W films. By using radio-frequency magnetron sputtering, we prepared a series of the three-layer films whose Fe₂VAl thickness ranged from 1 nm to 37 nm. The fine oscillation of reflectivity associated with the top W layer clearly appeared in synchrotron x-ray reflectivity measurements, indicating a less obvious mixture of elements at the boundary. The areal heat diffusion time, obtained from the time-domain thermoreflectance signal in the rear-heating front-detection configuration, reduced rapidly in samples whose Fe₂VAl layer was thinner than 15 nm. The ～ 10% mismatch in lattice constant between Fe₂VAl and W naturally produced the randomly distributed lattice stress near the boundary, causing an effective increase of boundary thermal resistance in the thick samples, but the stress became homogeneous in the thinner layers, which reduced the scattering probability of phonons.